Isomerization of cyclo-olefins



Patented Dec. 2, 1947 ISOMERIZATION OF CYCLO-OLEFINS Vladimir N. Ipatieff and Herman Pines, Chicago,

Ill., assignors to Universal Oil Products Company, Chicago, 111., a corporation of Delaware No Drawing. Application February 28, 1945, Serial No. 580,288

15 Claims. 1

In broad principle the present invention relates to a process for isomerizing a cyclic-olefinic hydrocarbon in which at least one carbon atom of the cyclic-hydrocarbon ring has two substituent groups attached thereto and at least another carbon atom of the ring with only hydrogen attached thereto. More specifically this invention relates to a process for isomerizing a gem di-substituted cyclic-olefinic hydrocarbon to produce therefrom a cyclic-olefinic hydrocarbon in which not more than one substituent group is combined with each carbon atom of the cyclic-hydrocarbon ring.

One object of this invention is to provide a process for isomerizing gem di-substituted cyclicolefinic hydrocarbons. A further object of this invention is to convert gem di-substituted cycloheXenes into ring substituted cyclohexenes in which not more than one substituent group is combined chemically with each carbon atom of the cyclohexene ring.

In one embodiment this invention comprises a process for isomerizing a gem di-alkyl cyclo-olefinic hydrocarbon which comprises reacting said hydrocarbon in the presence of an acid-acting catalyst to form a di-alkyl cyclo-olefinic hydrocarbon in which each of the alkyl substituent groups is attached to different carbon atoms in the cyclo-olefin ring.

In another embodiment this invention relates to a process for isomerizing a gem (ii-substituted cyclo-olefin by reacting said cyclo-olefin at conversion conditions in the presence of an aqueous solution of a mineral acid.

In a further embodiment this invention comprises a process for isomerizin a gem di-alkyl cyclo-olefinic hydrocarbon having in its rin structure at least one carbon atom with only hydrogen attached thereto which comprises reacting said gem di-alkyl cyclo-olefinic hydrocarbon in the presence of an acid-acting catalyst consisting of a hydrolyzable salt in contact with water, said isomerization resulting in the formation of a cyclo-olefinic hydrocarbon in which not more than one alkyl group is attached to each carbon atom in the cyclo-olefin ring,

The isomerization reaction involved in the process of our invention may be illustrated by the following equation in which R, R1 and R2 represent alkyl groups attached to a cyclohexene ring. Since R and R1 are attached to the same carbon atom of the cyclohexene ring, it is by definition a di-alkyl gem carbon atom. The starting materialfa gem di-alkyl cyolohexene, is isomerized in the presence of an acid-acting catalyst (represented by H+ in the equation) to a cyclohexene in which no carbon atom of the ring has attached thereto more than one alkyl group:

present invention is unique as distinguished from the prior art in that it concerns an isomerization involving the migration of one of the substituent groups, from a gem di-substituted carbon atom of a cyclic-hydrocarbon ring to a new position in the ring, said cyclic-hydrocarbon containing an unsaturated linkage either in a substituent group or in the hydrocarbon ring, but not in both the ring and the substituent involved in the isomerization at the same time.

The preferred starting material comprises gem cyclo-olefins in which the cyclo-olefin nucleus is a cyclopentene or a cyclohexene ring; however, the process is not necessarily limited to these cyclic hydrocarbons. It has been found, in general, that when the charging stock comprises a major proportion of gem cyclo-olefins in which the cyclo-olefin nucleus of these hydrocarbcns have fewer than five carbon atoms, one or more of the alkyl groups attached to the cyclo-olefin enter the cyclic hydrocarbon nucleus until a cyclohexene is obtained. In the products of these reactions can be found substantial yields of cyclohexenes where no such hydrocarbons were found in the analysis of the original starting material. Substituents R, R1 and R2 attached to the cyclic ring as in the type of compounds represented in the above equation may comprise the saturated or unsaturated cyclic hydrocarbon radicals, the saturated or unsaturated hydrocarbon chains, such as alkyl, alkenyl, or alkinyl groups and these may be normal, secondary, or tertiary radicals such as methyl, ethyl, vinyl, propyl, isopropyl, etc.

In the process of our invention the isomerizable compounds which may be treated according to the teachings of the present invention do not include those Which by reason of their structure cannot be isomerizable in this manner. For example, 1,1,2,3,4,5,6-heptamethyl-cyclohexene is not considered to be isomerizable by these methods to form a cyclohexene in which no carbon atom of than one methyl group.

The catalyst for the reaction involved in the present process includes an acid-acting substance in aqueous solution. The acid-acting catalyst comprises a member or members selected from the group consisting of an aqueous solution of an acid such as sulfuric, a phosphoric acid, hydrochloric, hydrobromic, etc. or a substance which reacts with water under favorable conditions of temperature and pressure to give an aqueous or vaporous medium of an acid-acting substance. This latter group of catalysts comprises salts which hydrolyze in contact with water to yieldinitially or develop during the course of. the reaction a solution or mixture having a measurable acidity. Such salts include magnesium. chloride, ammonium chloride, ferric chloride, hydrolyzable sulphates and phosphates such as ferric sulfate,

ammonium sulfate, monoand disodium phosphates, and many similar acid-acting salts. Other catalysts utilizable in the present process are the. acid-acting solid catalysts, such as silicaalumina combinations, prepared according to the methods employed in the preparation of catalysts for the cracking of petroleum or its fractions. These latter catalysts have been shown to have measurable acidities, and as such can be employed in effecting the isomerization specified in this process. Another solid acidic catalyst utilizable in the process of the present invention comprises the solid phosphoric acid catalysts, prepared by the chemical fixation of a phosphoric acid on a solid adsorbent, such as silica, a clay, kieselguhr, etc. The list of solid, acid-acting catalysts includes many more, known to those familiar with the art employing these catalysts.

The process of our invention may be operated to produce the isomerized olefins as such or the product of the invention may be made to yield convenient starting materials forsubsequent processes. be hydrogenated to yield the corresponding cycloalkane and the process terminated here for obtaining these valuable materials, or the cycloolefin may be charged to a dehydrogenation process for the production of the corresponding alkylated aromatic derivative.

While the process of the present invention may be effected in either batch or continuous. types of operation, it is usually conducted. on a continuous basis by withdrawing from the reaction zone a mixture consisting principally of the starting material and the isomerized product. The said mixture is withdrawn from the. reactor at substantially the same rate as charging stock is introduced into the reactor and may be withdrawn through a suitable separating device which may consist of means for fractionating or absorbing selected constituents, or the device may consist merely of a condenser for removing in one operation all of the products of the reaction. The recovered starting material may be recycled as such for further reaction or may have intermediate treatment as purification, concentration, etc.

The ratio of catalyst solution to hydrocarbons in the reaction zone depends upon the temperature, pressure, and particularly upon thenature of the charge stock. In general the ratio of aqueous catalyst solution to the reactant material charged is usually 1:1 on a volume basis but this ratio may be varied. between about 0.111 to-about 2:1. Certain values of these. ratios are found to be optimum, depending upon the particular charge and operating conditions- The aqueous catalytic solution ofv theabovementioned Thus, the isomerized cycle-olefin may acid-acting substances may range from very dilute to very concentrated solutions, but concentrations in the range of about 0.1% to about 10% of the acid-acting substance are preferred. Temperatures in the range of from about 100 to about 450 C. are operative but temperatures between about 200 to about 350 C. are preferred. Pressures may range between subatmospheric to superatmospheric, that is from a fraction of 1 atmosphere as the lower limit to about 100 atmospheres as the upper limit. It may, however, be found desirable to emplo low pressures in some casesto eliminate undesirable reactions.

The following example illustrates the results obtained. for a specific compound by the process of the present invention, although it is not intended to limit the scope of the invention in accordance with the conditions employed in the example:

55 g. of 2,2,4-trimethylcyclohexene-1 was heated for three hours at 375 C. with cc. of an aqueous 2% magnesium chloride solution in an autoclave of 850 cc. capacity. The product of the reaction was fractionall distilled, yielding 23 grams (41.8%) of material boiling at 139 to 152 C, and having an n equal to 1.4514. This fraction was hydrogenated at 60 to 66 C. to give 18 grams of product boiling at 139 to 144 C., and having an n equal to 1.4308. The hydrogenated product was converted to the corresponding benzene compound by dehydrogenation over platinized alumina, yielding 8 grams of material boiling at 166 to 167.5" C. and having an n equal to 1.5060. The dehydrogenated product was identified by preparation of the nitro derivative. This compound melted at 181 to 182 C., the melting point of the trinitro derivative of 1,2,4- trimethylbenzene.

We claim as our invention:

1. A process for isomerizing a cyclic-monoolefinic hydrocarbon having in the cyclic hydrocarbon ring, at least one carbon atom with two substituent groups attached thereto and at least one other carbon atom in the ring with only hydrogen attached thereto, which comprises treating said hydrocarbon in the presence of an acid-acting isomerizing catalyst to form a cyclic-monoolefinic hydrocarbon in which not more than one substituentgroup is in chemical combination with each carbon atom of the cyclic hydrocarbon ring.

2. A process for isomerizing a cyclic-monoolefinic hydrocarbon having in the cyclic hydrocarbon ring, at least one carbon atom with two substituent groups attached thereto and at least one other carbon atom in the ring with only hydrogen attached thereto, which comprises treating said hydrocarbon in the presence of an aqueous solution of an acid-acting isomerizing catalyst to form a cyclic-monoolefinic hydrocarbon in which not more than one substituent group is in chemical combination with each carbon atom of the cyclic hydrocarbon ring.

3. A process for isomerizing a cyclic-monoolefinic hydrocarbon having in the cyclic hydrocarbon ring at least one carbon atom with two substituent groups attached thereto and at least another carbon atom in the ring with only hydrogen attached thereto, which comprises treating said hydrocarbon in the presence of a catalyst comprising essentially an aqueous solution of a mineral acid to form a cyclic-monoolefinic hydrocarbon in which not more than one substituent group is in chemical combination with each carbon atom in the cyclic hydrocarbon ring,

4. A process for isomerizing a cyclicmono-' olefinic hydrocarbon having in the cyclic hydrocarbon ring at least one carbon atom with two substituent groups attached thereto and at least another carbon atom in the ring with only hydrogen attached thereto, which comprises treating said hydrocarbon in the presence of an aqueous solution of a hydrolyzable acid-acting salt to form a cyclic-monoolefinic hydrocarbon in which not more than one substituent group is in chemical combination with each carbon atom in the cyclic hydrocarbon ring.

5. A process for isomerizing a cyclic-monoolefinic hydrocarbon having in the cyclic hydrocarbon ring, at least one carbon atom with two substituent groups attached thereto and at least another carbon atom in the ring with only hydrogen attached thereto, which comprises treating said cyclic-monoolefinic hydrocarbon at a temperature of from about 100 to about 450 C. in the presence of an aqueous solution of an acidacting catalyst to form a cyclic-olefinic hydrocarbon in which not more than one substituent group is in chemical combination with each carbon atom of the cyclic hydrocarbon ring 6. A process for isomerizing a cyclic hydrocarbon, the cyclic portion of the said hydrocarbon being a cyclo-alkyl group having in the ring at least one carbon atom With only hydrogen attached thereto, and at least another carbon atom in said ring with two hydrocarbon substituent groups attached thereto, one of which is an unsaturated hydrocarbon group, which comprises treating said cyclic hydrocarbon in the presence of an aqueous solution of an acid-acting catalyst to form a cyclic hydrocarbon in which not more than one substituent group is in chemical combination with each carbon atom of the cyclic hydrocarbon ring.

7. A process for isomerizing a gem di-alkyl cyclohexene which comprises reacting said cycloheXene in the presence of an aqueous acid-acting catalyst to form a cyclohexene hydrocarbon having not more than one alkyl group in chemical combination with each carbon atom of the cyclohexene ring.

8. A process for isomerizing 2,2,4-trimethylcyclohexene-l which comprises reacting th said hydrocarbon at a temperature of between about- 100" and about 450 C. and in the presence of an aqueous magnesium chloride solution under such conditions that 1,2,4-trimethyl-cyclohexene-5 is produced therefrom.

9. A process for iscmerizing a gem di-substituted cyclic-olefinic hydrocarbon containing at least one unsubstituted carbon atom in the ring and containing only a, single olefinic double bond per molecule, which comprises contacting said bydrocarbon at isomerizing conditions with an acidacting isomerization catalyst to effect migration of at least one of the gem substituents thereby forming a cyclic-monoolefinic hydrocarbon containing not more than one substituent on each carbon atom in the ring.

10. A process for isomerizing a gem di-substituted cyclic-olefinic hydrocarbon containing at least one unsubstituted carbon atom in the rin and containing only a single olefinic double bond per molecule, which comprises contacting said hydrocarbon at a temperature of from about C. to about 450 C. with an acid-acting isomerization catalyst to effect migration of at least one of the gem substituents thereby forming a cyclic-monoolefinic hydrocarbon containing not more than one substituent on each carbon atom in the ring.

11. The process of claim 9 further characterized in that said gem di-substituted cyclic-olefinic hydrocarbon comprises a gem di-substituted cyclohexene,

12. The process of claim 9 further characterized in that said gem 'di-substituted cyclic-olefinic hydrocarbon comprises a gem di-alkyl cyclohexene.

13. The process of claim 9 further characterized in that said catalyst comprises an aqueous solution of an acid-acting salt.

14. The process of claim 9 further characterized in that said catalyst comprises an aqueous solution of a mineral acid.

15. The process of claim 9 further characterized in that said catalyst comprises a silicaalumina composite.

VLADIMIR N. IPA'I'IEFF. HERMAN PINES.

REFERENCES CITED The following references are of record in the file of this patent:

Eglofi et al., Isornerization of Pure Hydrocarbons, pages 328 to 9 (1942). (Copy in Div. 31.) 

